yeah the doc says to deploy where wasp is, but it needs to be deployed to the ump robot.
Also it is version specific, so webservices_rest 9.0.2 will not work with uim 8.51
the 404 is most likely due to it being deployed to the wrong system or using the wrong system in the url
another test is:
http://<umpserver IP address or name>:8080/rest/version-info
or try it without the port:
http://<umpserver IP address or name>/rest/version-info